Devices for delivering a medical or therapeutic fluid, such as, for example, insulin pumps, are widely used. In a number of applications, in particular in the self-therapy of diabetes mellitus via continuous subcutaneous insulin infusion (CSII), the devices are used and operated directly by a patient, e.g. by a person with diabetes.
Most of these devices include or are designed to receive an administration container for the medical or therapeutic fluid. Typically, the administration device is realized as a cartridge having a cartridge body with a longitudinal axis and a piston that is movable along the longitudinal axis inside the cartridge body. In order to apply the medical or therapeutic fluid, the piston is coupled to a drive configured to displace the piston in a controlled way, such that fluid in the administration is forced into a catheter or infusion line. This type of device is known as “syringe driver”. Initially, the administration container is empty and needs to be filled by the patient prior to use.
Patients using devices for delivering a medical or therapeutic fluid often have preferred medical or therapeutic fluids, which are available in supply containers of different forms. Insulin, which is a medical or therapeutic fluid, is available, for example, in so called vials, which are supply containers typically made from glass and having an access to the insulin on one side through a septum, a membrane that can be perforated or punctured by a cannula, typically a syringe cannula. Insulin is also distributed in so called pen-cartridges, which generally are cylindrical supply containers having on one side also a septum for accessing the insulin, and having on the other side a movable piston. Pen-cartridges are designed for use in dedicated injection devices, so-called pen-type injectors.
For use in delivery devices such as in insulin pumps, the medical or therapeutic fluid has to be filled from the supply container into the administration container, as explained above. In dependence of the design of the administration container and the type of supply container, a variety of filling procedures exist. However, filling procedures are particularly disliked by many patients, as they are known to be cumbersome and to involve a number of delicate handling steps. The filling procedure is especially critical for persons with additional handicaps such as tactile or visual disabilities, which often result as a long-term side effect of diabetes. Depending on the filling volume, the type of the medical or therapeutic fluid, and/or the user's individual needs, it is required to fill an administration container every few days, in particular in diabetes therapy.
Manually filling an administration container with a medical or therapeutic fluid from a vial requires temporarily attaching a syringe-handle to a movable piston of the administration container, thus temporarily modifying the administration container into a syringe. With the syringe obtained, an air pressure is generated inside the vial. In a second step, the air pressure presses the medical or therapeutic fluid from the vial into the syringe. Filling from a pen-cartridge is provided by applying a pushing pressure on the moveable piston of the pen-cartridge, such that the medical or therapeutic fluid is depleted from the pen-cartridge into the administration container. In filling procedures, particular attention is given to avoid formation of air bubbles that are likely to occur during the procedure and need to be removed prior to use of the filled administration container.
WO 2006/048114 discloses a filling process for filling a container with an injection or infusion fluid. A suction device is actuated by a motor to suck the injection or infusion fluid into the container. A vibration unit may be actuated to remove air bubbles from the liquid after filling the container. Filling may be performed by an insulin pump comprising an insulin container and configured to deliver insulin to a patient. The supply container, for example a flexible container, must be designed such, that suction of the medical or therapeutic fluid from the supply container is enabled.
EP 2 332 600 discloses filling a container with a liquid drug from a drug reservoir. The container is connected to the drug reservoir. The inside volume of the container is reduced, thereby displacing a gaseous medium, typically air, from the container into the drug reservoir. In a next step, the inside volume of the container is increased, thereby displacing liquid drug from the drug reservoir into the container. The steps of reducing and increasing the inside volume of the container are performed successively more than once, thus realizing a multi-step filling procedure of the container. By multi-step filling, the operational pressure, and, accordingly, the pressure gradient, is reduced as compared to a single-step filling procedure, thus avoiding the generation of air or gas bubbles. The filling procedure as disclosed in EP 2 332 600, however, is not suited for pen-cartridges as drug container, since the movable piston of the pen-cartridge may be pushed out of pen-cartridge when displacing gaseous medium from the container into the pen-cartridge.